[csande17]

> Why does a network-ban even need to exist? There is no algorithm that presents your feed with posts from other servers. You only see who you follow.

Mastodon servers do often have a "federated timeline" that shows you all the posts from servers your instance knows about. People can also send you unsolicited messages by replying to you or @-mentioning you.

> Who is the person who has the final say which server may be part of the fediverse?

I don't think there's really a single person with the authority to ban someone from the whole fediverse; your instance admins always have the final say about whether their instance talks to another instance. But things like shared blocklists mean that, in the vast majority of unambiguous spam or illegal content cases, only one person actually has to respond to them directly.

[xigoi]

> People can also send you unsolicited messages by replying to you or @-mentioning you.

You can deal with that by blocking them personally. No need for a guardian angel.

[lupire]

You can't block everyone bad because you don't know who they are until after they spam you. Last month I got 100 spam texts from the same sender ([Redacted] Political Party) using a different phone number for each.